New Study Reveals Source of Purple Spots On Vatican Scroll

Scientists have pinpointed the reason why there are purple spots on a famous Vatican Secret Archives manuscript.

Those familiar with Vatican history may recognize the name Laurentius Loricatus — some 800 years ago, he was a teenage soldier who had killed another man by accident, then spent the next 34 years in an Italian cave as penance for what he had done. This penance, as noted by Live Science, included using a hot iron to burn his face and wearing a hooked chain-mail shirt. And while his story was documented on a 16-foot-long piece of parchment now found in the Vatican Secret Archives in Vatican City, several parts of that document have since been covered by purple splotches.

The reason why Laurentius Loricatus’ story on the Vatican scroll has purple spots has finally been revealed by a team of Italian researchers. According to University of Rome Tor Vergata ecotoxicologist Luciana Migliore, the splotches are similar to the stains found on parchments made of animal skins. But what was really surprising was the actual source of the stains, as Migliore recounted in an interview with Gizmodo.

“I found marine microbes. Where did they come from, in a goat parchment that had been written eight hundred years ago? This was absolutely surprising.”

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The process the researchers used to determine why Loricatus’ Vatican scroll had purple spots was a long, drawn-out one, yet one that had also led them to come up with their shocking conclusion. Small squares of the parchment that had already been detached from the manuscript were analyzed, with Migliore and her colleagues isolating the DNA and sending it to a Texas-based lab for further processing.

Looking at both stained and unstained portions of the scroll, the Texas lab found 957 types of bacteria on the purple spots, and 407 types on the unblemished part, with only 140 of those types being among the 1,224 species shared between both stained and unstained portions. Gammaproteobacteria was identified as the most common form of bacteria on the Vatican scroll’s purple spots.

[Image by ktsdesign/Shutterstock]

As the parchment was made out of goat skin, which is usually preserved with salt brines, the researchers believe that the brine was the active agent that allowed the purple microbes to emerge, despite the fact that curing with salt brines kills off most microbes known to eat away at flesh. After being cured with the salt, the parchment was then contorted and scraped, making it salty outside and not that salty inside, with the collagen inside providing a home to the bacterial colonies. The scrolls were then read and kept at different monasteries over the next several hundreds of years.

Monasteries are subject to fickle temperature changes and moisture, and that’s why the researchers noted that the setting was perfect for the purple bacteria to thrive. But since these microorganisms ultimately had to die after running out of salt to feed on, their corpses would have served as food for the next generation of gammaproteobacteria to make themselves at home within the parchment.

The new study, however, is not without its share of limitations. Speaking to Gizmodo, Guadalupe Pinar of the Universität für Bodenkultur in Austria commended the researchers for using state-of-the-art techniques in analyzing the Vatican scroll and determining the source of its purple spots. But he added that there is a possibility of missing data, as the scientists worked with only one subset of DNA sequences. Lastly, he suggested that the researchers lucked out when they found individual pieces of the parchment; it would have been necessary to tear off the parchment in most other cases.